Notes on each item:
A. Meeting rooms go fast. Better reserve that immediately after the date and time for the meeting is decided.
B. Food preparation takes planning and lead time to have time to buy supplies and fix the food...at least a week's lead time would be the minimum in most cases.
C. Email reminders can be set up to go at certain intervals...one today announcing next week's meeting. Another next Thursday as a reminder that it is tomorrow and then another on Friday morning that the meeting is "today at lunch time."
D. Ice will have to be at the last minute...but you need to make plans for the bowl...unless the caterer is bringing it.
E. The office supply order needs time to be processed through the Purchasing Department, ordered, and delivered. Better order it today, tomorrow at the latest.
F. Audio-Visual Department requires at least 24 hours notice...so you have bit of time...but don't forget to place the request for service.
G. Before you can put the agenda together, you need to consult your boss for items that need to be on the agenda. It is usually a good idea to wait to print the agenda until fairly close to the meeting to allow for last minute additions.
Another way to set priorities is by what you can accomplish rapidly and move on to the next item that needs to be done. Reserving the meeting room, placing the food order, and setting up the AV equipment request will probably take 15 minutes each and need to be done as soon as possible.
Might as well knock those out as soon as those offices open for business and move on with the rest of your day. If you need to order office supplies anyway, just add the ones that are needed for the meeting and send it off in time to be back for the meeting.
By knowing the ultimate goal, you can break down the steps needed to reach the goals and objectives of the company, your boss, and you. If you find yourself getting distracted or overwhelmed, refocus on the goal and get back on track.